Where a cylindrical member rotates within a complementary cylindrical bore, the useful life of the parts can be extended by providing a counter sink at one of the bore into which is inserted a tubular, hardened wear ring. For example, machines used to cut hard surfaces such as concrete and asphalt have a rotatable cutting wheel with a plurality of cutting tools mounted on the wheel which are moved against a hard surface to advance the cut. Each of the cutting tools has a cylindrical shank which is rotatably mounted in a complementary cylindrical aperture in a mounting block. As disclosed in my co-pending application, Ser. No. 09/121,726 filed Jul. 24, 1998, the useful life of a tool and the mounting block can be extended by providing a tungsten carbide tubular insert at the forward end of the aperture in the mounting block or holder.
It is customary to use a braze to retain parts, such as a tubular insert fitted in a countersink at the end of a cylindrical aperture. The brazing process consists of providing a ring of braze material which is fitted between the inner surface of the countersink and the outer surface of tubular sleeve. The ring of braze material prevents the hardened ring from becoming seated within the countersink until the braze material is heated and melts, after which the ring can be forced into the countersink until it has become seated. After the parts cool, a substantial portion of the braze material should remain between the inner surface of the countersink and the outer surface of the insert to retain the parts in the assembled relationship. I have found, however, that when the braze material melts and a tubular insert is forced into a countersink most of the liquefied braze material flows into the cylindrical bore leaving an insufficient amount of braze material to retain the parts in the assembled relationship. When a tungsten carbide insert is brazed into a countersink around the bore of a tool block, as described above, it has been found that the braze will fail when the tool is subjected to the forces required to cut hard material such as concrete or asphalt.
An improved method is therefore needed for brazing of tubular parts in nested relationship in which a greater portion of braze material would be retained between the parts.